Non-cracking tufted carpet with nonwoven secondary backing and method of making same



Dec. 3, 1968 R. I. LACY v 3,414,458

NON-CRACKING TUFTED CARPET WITH NONWOVEN SECONDARY BACKING AND METHOD OFMAKING SAME Filed Dec. 16, 1965 1N VENTOR RICHARD l. LACY ATTORNEYUnited States Patent 3,414,458 NON-CRACKING TUFTED CARPET WITH NON-WOVEN SECONDARY BACKING AND METHOD OF MAKING SAME Richard I. Lacy,Wilmington, Del., assignor to E. I. du Pont de Nemours and Company,Wilmington, Del., a corporation of Delaware Filed Dec. 16, 1965, Ser.No. 514,414 3 Claims. (Cl. 161-67) This invention relates to tuftedcarpets and in particular to a process for the production of improvedcarpets having a nonwoven secondary backing.

Tufted carpets are composite structures in which the yarn forming theloops or pile in the surface of the carpet is needled through a basefabric (primary carpet backing) such as woven jute, burlap, or anonwoven fabric such as is described in British Patent 989,591. The basesegments of the yarn loops are bonded firmly to the underside of theprimary carpet backing by means of a suitable adhesive. The adhesive ispreferably applied as an aqueous dispersion of an elastomeric material,such as a latex of natural or synthetic rubber. In order to improve theappearance, dimensional stability, bulk and body of the tufted carpet,and also to provide a tough covering which further protects the primarycarpet backing and the base segments of the yarn loops, a secondarybacking is customarily adhered to the composite structure by means ofthe same latex adhesive used to bond the yarn loops to the primarybacking. The secondary backing may be either a woven fabric composed ofa material such as jute or twisted paper strands or a nonwoven fabric.Nonwoven fabrics, for example, those composed of bonded polypropylenefibers, possess several advantages as secondary backings, particularlyin regard to their low cost and improved dimensional stability atvarying relative humidities.

A disadvantage of nonwoven secondary backings, however, is theoccurrence of cracking or buckling of the backing when the carpet isbent. This cracking occurs mainly along lines parallel to and betweenthe tuft rows when the carpet is bent along a similar bending axis. Dueto the structure of the carpet, cracking does not occur as readily alonglines perpendicular to the tuft rows.

It has been found that the cracking can be eliminated by using a higherlevel, for example, twice as much, of a standard latex-adhesiveformulation but this entails an economic penalty. In addition, thesethick coatings are difficult to dry on present commercial equipment ateconomically attractive speeds. It has also been found that crackingbehavior can be improved by the use of latex-adhesive formulationscontaining a higher ratio of filler to rubber, for example, 4:1 ratherthan 23:1 of the standard latex formulations. Filler refers to thepigments of both the hiding and extender types. Carpets produced withadhesives having the higher-filler formulations, however, are deficientto resistance to fuzzing and pilling of the pile yarn as Well astuft-pullout strength.

This invention provides an economically attractive method for obtainingnoncracking tufted carpets with nonwoven secondary backings whilemaintaining a good balance of physical properties. The method of thisinvention comprises coating the underside of a. tufted primary carpetbacking with a latex formulation having a filler-torubber ratio of from0 to 1:1 on a weight basis, applying a second coating of a latexformulation having a filler-torubber ratio of at least 2:1, bringing anonwoven fabric into contact with the second coating and drying theresulting structure.

The first coating should have a viscosity of 10,000 cps. or less, and isapplied at a pickup rate of about 5 to oz./yd. (170 to 340 g./m. Thiscoating provides fuzzand pill-resistance to the pile yarn and improvedtuftpullout strength. If desired, an unmodified elastomeric latex, thatis, one containing no filler, can be used as th first coat.

The second coating should have a viscosity of at least about 10,000 cps.or more, and is applied at a pickup rate of about 12 to 25 oz./yd. (410to 850 g./m. This coating fills the spaces between the tuft rows, andbonds the secondary backing to the tufted primary backing. Presence ofthe second coating improves cracking behavior. In order to obtainadequate adhesion between the tufted primary backing and the secondarybacking, the filler-torubber ratio of the second coating should notexceed about 6: 1.

The latex formulations which are used as the first and second coatingsin this invention are similar to the standard latex formulations nowused as backing adhesives except that they differ in thefiller-to-rubber ratios. Any of the known elastomers are suitable foruse in the adhesive formulations including natural rubber, syntheticpolyisoprene, unmodified and carboxyl-modified butadiene/ styrenecopolymers, butadiene/acrylonitrile copolymers, chloroprene andpolyisobutylene. A typical, standard latex formulation is shown below(components):

Water (to a solids content of 65%).

Carboxyl-modified butadiene/ styrene copolym'ers are self-curing andthus can be formulated without the sulfur curing system. A typicalformulation of this type is shown below (components):

Parts (dry basis) Carboxyl modified butadiene/styrent copolymer latexTetrasodium pyrophosphate (dispersing agent) 0.25 Whiting (extenderpigment) 200 Thickener (e.g. sodium polyacrylate) 0.8

Water (to a solids content of 68% Other suitable extender pigmentsinclude clay, talc, asbestos mica, sand and glass microbeads. Theviscosity of the formulation can be adjusted by use of known thickenerssuch as sodium carboxymethylcellulose, polyvinyl alcohol, sodiumpolyacrylate and the natural water-soluble gums.

The coatings can be applied by the standard methods known in the artincluding spraying, roller coating, knife coating and the like. Thefigure is a schematic diagram of a suitable procedure for carrying outthe coating process of this invention. In the figure, tufted primarycarpet backing 10 is coated on the underside with latex formulation A byapplicator roll 11, the excess coating is removed by doctor blade 12,then a coating of latex formulation B is applied by applicator roll 13,the coating is smoothed with doctor blade .14, and the secondary carpetbacking 15 is then brought into contact with the wet second coating. Thestructure is'passed between lowpressure rolls 16 and 17 to press thesecondary backing firmly against the second coating. The compositestructure is then dried at about -170 C. in oven 18. If

desired, the carpet may be supported in a tenter during the dryingoperation. Idler rolls 19 are used to provide the required tension andguidance for the tufted primary carpet backing during the coating steps.

The process of this invention can be used with advantage with all knowntypes of nonwoven fabrics which, except for their cracking behavior, aresuitable as secondary carpet backings. A particularly preferred materialfor this application is a nonwoven fabric of self-bonded, continuousfilaments of polypropylene. In the preparation of such a fabric, anunbonded nonwoven web of polypropylene filaments, such as can beproduced by the process described in British Patent 932,482, can bepressed between heated embossing rolls at 140 to 190 C. to effectsimultaneous bonding and formation of a decorative pattern on thesurface of the sheet. Other bonded nonwoven fabrics of continuousfilaments or staple fibers of such organic polymers as the polyamides,polyesters, polyacrylonitrile, etc. are also suitable. Although nonwovenfabrics of the synthetic, organic polymers are preferred because oftheir improved dimensional stability at varying relative humidities,nonwoven fabrics of natural and regenerated fibers can also be used. Thenonwoven fabric used in the process of this invention must be bonded.Excessive fuzzing of the exposed surface of the secondary carpet backingis observed with unbonded webs since the second coating in thisinvention does not completely impregnate and bond the fibers in thesecondary backing but instead merely serves to bond the secondarybacking to the tufted primary backing. The bonding of the nonwovenfabric to be used as a secondary carpet backing can be effected bymethods well-known in the art and accordingly they are not furtherdescribed herein.

The invention will be further understood by reference to the followingcontrol experiments and examples.

Experiment A To the underside of a nonwoven primary carpet backingtufted with about 20 oz./yd. (680 g./m. of bulked continuous filamentnylon carpet yarn (denier, 3700) is applied a 24 oz./yd. (810 g./m.coating of a standard latex formulation having a filler-to-rubber ratio(weight basis) of 2:1, a solids content of 65% and a viscosity of 8000cps. The elastomeric material is a carboxyl-modified butadiene/ styrenecopolymer. A secondary backing in the form of a self-bonded and embossednonwoven fabric composed of continuous polypropylene filaments is thenbrought into contact with the latex coating as soon after application ofthe coating as possible. The laminate formed is passed between twolow-pressure rolls and then dried with the pile yarn down at 130 C. for30 minutes.

Upon bending the finished sample along an axis parallel to the tuftrows, creases in the secondary backing are very evident and are causedby collapse of the hacking into the voids between the tuft rows. Thisphenomenon is termed cracking. Another evidence of the cracking is theundesirable grin-through of the primary carpet backing when the bentcarpet is viewed from the pile side.

Experiment B Experiment A is repeated except that the amount of latexcoating is increased to 3540 oz./yd. (1180-1350 g./m. After drying, thelaminated structure does not exhibit the cracking observed in ExperimentA. This demonstrates that cracking can be limited with high loading of astandard latex formulation.

Experiment C A finished carpet sample is prepared as in Experiments Aand B except that a modified latex formulation having a filler-to-rubberratio of 4:1 is used. The increased ratio is obtained by adding clay tothe standard latex formulation of Experiment A and diluting with waterto maintain the solids level at 65%. The viscosity of the modifiedformulation is over 12,000 cps. The latex formulation is applied at alevel of 28 oz./yd. g./m. This slightly higher level compared toExperiment A is of no economic consequence because of the lower unitcost of the high-filler-content formulation. After the standard dryingstep, the sample does not crack. Compared to the products prepared inExperiments A and B, however, it is deficient in fuzzand pill-resistanceof the pile yarn and tuft-pullout strength.

EXAMPLE 1 A tufted primary carpet backing as in Experiment A is given aninitial light coating (about 7 oz./yd. 240 g./m. of an unpigmented latexhaving a viscosity of 5000 cps. and containing 50% solids(carboxyl-modified butadiene/styrene copolymer). This first coating isimmediately followed by a second coating of a high-fillercontent (4:1filler-to-rubber ratio), high-viscosity (13,000 cps.) latex formulation.The total weight of the two coatings is 28 oz./yd. (950 g./m. A nonwovencarpet backing is then applied and the laminate dried as in thepreceding experiments. The finished carpet sample is acceptable in allrespects. It does not crack and it exhibits good fuzzand pill-resistanceand adequate tuft-pullout strength. The first latex coating penetratesthe yarn bundles behind the primary backing and to some extent withinsaid backing, and prevents fuzzing and pilling and provides tuft-pulloutstrength. The second latex coating fills the voids between the tuft rowsand prevents cracking that occurs on collapse of the nonwoven secondarybacking.

- EXAMPLE 2 An initial coating of a latexing compound containing acarboxyl-modified butadiene/styrene copolymer and having a filler(whiting)-to-rubber ratio of 1:1, a solids content of 68%, and aviscosity of 10,000 cps. is applied to the back of a tufted primarycarpet backing as in Experiment A. This is immediately followed by asecond coating of a latexing compound having a filler-to-rubber ratio of2.5: 1, a solids content of 68%, and a viscosity of 10,000 cps. Thefirst coating is applied at a level of 10 oz./yd. (340 g./m. and thesecond coating, at 14 oz./yd. (470 g./m. A nonwoven secondary backing isthen applied and the composite structure dried as in Experiment A. Thefinished carpet sample is acceptable in all respects.

What is claimed is:

1. A method for preparing a tufted carpet having a nonwoven secondarybacking and resistant to cracking comprising coating the underside of atufted primary carpet backing with a latex formulation having afiller-torubber ratio of from 0 to 1:1 on a weight basis, applying asecond coating of a latex formulation having a filler-torubber ratio ofat least 2:1, bringing a bonded nonwoven fabric into contact with thesecond coating and drying the resulting structure.

2. The process of claim 1 wherein the first coating has a viscosity nogreater than about 10,000 cps. and is applied at a pickup rate of about5 to 10 oz./yd. and the second coating has a viscosity of at least about10,000 cps. and is applied at a pickup rate of about 12 to 25 oz./yd.

3. A tufted carpet produced by the process of claim 1.

References Cited UNITED STATES PATENTS 3,007,836 11/1961 McNamara et a1156-310 3,060,072 10/1962 Parlin et al. l6l66 XR 3,166,465 1/1965 Rahmesl6166 3,227,574 1/1966- Mohr 1l745 ROBERT F. BURNETT, Primary Examiner.

R. H. CRISS, Assistant Examiner.

1. A METHOD FOR PREPARING A TUFTED CARPET HAVING A NONWOVEN SECONDARY BACKING AND RESISTANT TO CRACKING COMPRISING COATING THE UNDERSIDE OF A TUFTED PRIMARY CARPET BACKING WITH A LATEX FORMULATION HAVING A FILLER-TORUBBER RATIO OF FROM 0 TO 1:1 ON A WEIGHT BASIS, APPLYING A SECOND COATING OF A LATEX FORMULATION HAVING A FILLER-TORUBBER RATIO OF AT LEAST 2:1, BRINGING A BONDED NONWOVEN FABRIC INTO CONTACT WITH THE SECOND COATING AND DRYING THE RESULTING STRUCTURE.
 3. A TUFTED CARPET PRODUCED BY THE PROCESS OF CLAIM
 1. 